BASIS OF MYOCARDIAL ELASTICITY DERIVED FROM CARDIAC MRI IN A SWINE MODEL OF ISCHEMIC HEART FAILURE

Abstract

Background: Echocardiography and ejection fraction (EF) are the standard for assessing cardiac function in patients with myocardial infarction (MI) and chronic heart failure (CHF). Imaging modalities such as cardiac CT and MRI provide more detailed evaluation, offering superior spatial resolution and tissue characterization. Wall strain, measuring myocardial deformation, reflects contractile function as a percentage change in length. Wall stress represents the force per unit area on the myocardium, as an evaluation of left ventricular (LV) afterload. In this study, we combine strain and stress analysis to explore regional myocardial mechanics, potentially unveiling subtle changes in cardiac function post-MI. Purpose: We hypothesize that the combined analysis offers a more detailed assessment of regional wall motion abnormality than conventional imaging measures alone. Young's Modulus is the principle that relates strain and stress and defines cardiac elasticity. Methods: Male Yucatan mini-swine underwent 90-minute left anterior descending (LAD) coronary artery balloon occlusion-reperfusion (N = 13). Cardiac MRIs were performed pre-MI and 1-month post-MI. Endocardial and epicardial contours were analyzed at systole and diastole. Peak longitudinal, circumferential, and radial wall strain (LWS, CWS, and RWS) values were generated using the AHA 17-segment model. End systolic and diastolic wall stress (ESWS and EDWS) were calculated using LaPlace's law. Linear regression analysis was performed on paired wall stress and strain values. Results: At baseline there was no significant difference between Young's Modulus in the inferolateral and anteroseptal segments. Between baseline and 1-month post-MI, there was a significant increase in Young's Modulus across both regions. At 1-month post-MI there was a significant increase in Young's Modulus between inferolateral and anteroseptal segments. Conclusions: This study defines the effects of regional wall motion abnormalities on LV wall stress and strain after MI showing changes in the infarcted region as well as the non-infarcted area. The ability to quantify regional and directional cardiac elasticity non-invasively is a novel parameter that warrants further study. This approach could enhance early detection of heart failure progression and guide personalized treatment strategies in heart failure management. Prior research has explored the in-vitro characteristics of cardiac elasticity, but there is limited research that details these changes in-vivo that occur after MI or other fibrotic driven processes.